QM gap(less) Quantum Phase Transitions

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In quantum mechanics, the spectral gap of a system is the energy difference between its ground state and its first excited state. ... In solid-state physics, the most important spectral gap is for the many-body system of electrons in a solid material, in which case it is often known as an energy gap.

At very low temps. ( absolute zero , ) This gap can become " gapless " .

It takes the minutest amount of energy to reach a Quantum Phase transition ; without heat .

Now that's very interesting , is it not ? I think so .

About a year ago I bought this Issue of Scientific American ( special report , Oct./2018 ) ; The Unsolvable Problem . About a month ago I finally started to read the article .

Phase transition ; material goes through sudden and dramatic property change. ( Ice to liquid ) .

But at extremely low temps. Absolute zero ; an insulator can become a superconductor by changing the magnetic field around the material or by pressure ; as well a soild can become a superfluid .